David Foster's daughter poked fun at his engagement on Instagram.

The 68-year-old musician got down on one knee to propose to his girlfriend Katharine Mcphee, 34, during a recent trip to Italy and now his daughter Erin, 35, has given her view on the engagement.

Under a picture of David and Katharine on holiday, Erin quipped ''Mommmyyy'' alongside three red heart emojis.

The comment comes after a source claimed David is thrilled that Katharine is close with his children.

They said: ''David's children are what is most important to him in his life, so the approval of his children was key to making this a lifetime choice. Katharine became friends with his kids and they are thrilled she is part of his life. She immediately hit it off with his children, and that is what sealed the deal for him. Their engagement was a beautiful thing. Everyone is thrilled for them and can't wait to celebrate.''

David and Katharine have had a ''special bond'' from the start.

The source shared: ''From the very beginning, he and Katharine had a special bond. David took a lot of time off work to spend with Katharine. He is dedicated to his work, but he didn't want to miss out on any time with Katharine, so it was worth it for him ...

''There is no question that David is a hopeless romantic, but we thought David would never marry again after the difficult time he had at the end of his marriage to Yolanda. Four times is a lot of weddings and he wasn't planning on having more kids. He and Yolanda went through an incredibly bumpy time and he threw himself into his work. He seemed unhappy then. Soon after he started dating Katharine, he did a complete turn around and actually is quite starry-eyed. He fell in love immediately. It was as if it was meant to be.''